1. Field of the Invention
The present invention is directed generally to an apparatus and method of monitoring a subject and providing feedback thereto and, more particularly, to an apparatus and method of monitoring a subject and providing informational feedback thereto.
2. Description of the Background
Driver drowsiness poses a major threat to roadway safety and the problem is particularly severe for commercial motor vehicle (CMV) drivers. There are approximately 1.6 million truck tractors and 3.6 million trailers used in the motor carrier industry today. CUT's are involved in approximately 200,000 crashes each year. A recent analysis of the problem size estimates that fatigue related crashes constitute: (1) 0.71% to 2.7% of all police reported crashes involving CUT's; (2) 3.2% to 7.6% of all fatalities associated with CUT crashes; and (3) 15% to 36% of all crashes fatal to the CUT driver. As evident in these statistics, fatigue-related crashes tend to be severe. A typical fatigue related crash involves the CUT drifting off the roadway without brake application (run-off road crash). These crashes often occur early in the morning (between 2:00 AM and 6:00 AM) in light traffic conditions.
Thus, it may be desirable to have a drowsiness monitor and feedback device that promotes an understanding of fatigue, the potential consequences of driving while drowsy, and that provides guidance to drivers for managing fatigue. A common thread for addressing fatigue in any work environment is basic human physiology, in particular the need for sleep and the influence of natural circadian rhythms. If drivers are obtaining sufficient sleep, their alertness and performance will be optimized. If, however, drivers are receiving insufficient sleep, their alertness and performance will degrade accordingly.
A driver's alertness and corresponding performance levels also will cycle with the normal circadian rhythms. Performance degradation is most likely to occur during the natural circadian low points that occur for most people between 2:00 AM and 6:00 AM. A number of management structures have been proposed to promote fatigue management, safety and responsibility on the part of the driver. Fatigue, however, is illusive and often ill-defined, making management of fatigue qualitative and often based on indirect measures such as total time off-duty, etc. The problem is that decision-makers are often faced with too few facts and too many options.
It is known in the art to monitor a subject's eyes, such as to measure “PERCLOS” (Percent Eyelid Closure). PERCLOS is a measure of the proportion of time that a subject's eyes are closed and generally is defined as the proportion of time that a subject's eyes are closed either completely or beyond a predetermined point over a specified period. For example, PERCLOS may be the measure of the proportion of time that a subject's eyes are between 80% and 100% closed. Often, the measurement of PERCLOS must be done manually, such as by videotaping the subject, reviewing the tape, and measuring the subject's PERCLOS. Such a method, of course, may not be practical for many applications.
Another method of determining PERCLOS involves the use of an image sensor, such as a video camera, and image processing software to monitor the subject, determine the location of the subject's eyes, and determine the subject's PERCLOS. That method, however, is time consuming and often cannot be performed in real time, thereby prohibiting it from being used to determine the drowsiness of a driver of a motor vehicle. One attempt to overcome that problem is to monitor only a portion of the subject's face, the portion containing the subject's eyes, thereby reducing the amount of processing required to determine PERCLOS. That approach, however, creates another problem. The problem arises because the subject's eyes must be tracked as they move to monitor the road and as the subject's head and body move. Often, however, the subject moves quickly and the subject's eyes cannot be tracked. As a result, the prior art devices must search for the subject's eyes and, until the subject's eyes are located, the prior art devices cannot determine PERCLOS.
Another deficiency with various aspects of the prior art, regardless of whether the subject's entire face or only the subject's eyes are monitored, is that some prior art devices have difficulty finding and monitoring the subject's eyes. For example, the prior art devices may not be able to distinguish between the subject's eyes and other sources of light and reflected light, such as is caused by dashboard lights, lights from other vehicles, and street lights. Those problems may be exaggerated when the subject is wearing glasses.
Another method for determining PERCLOS involves monitoring the eyes and entire face of a subject in real time and is insensitive to other sources of light. A method and apparatus of monitoring a subject's eyes having such features is described in U.S. Pat. No. 6,082,858 to Grace et al., which is incorporated herein by reference in its entirety.